Natriferic and hydrosmotic effects of neurohypophysial peptides and their analogues in augmenting fluid uptake by Bufo melanostictus.
1. The effect of intramuscular injection of 8-arginine vasotocin, 8-arginine vasopressin, 8-lysine vasopressin, oxytocin, 8-ornithine oxytocin and 8-ornithine vasopressin on fluid uptake across the skin was studied in the live toad, Bufo melanostictus, bathed either in distilled water or in NaCl solution (0.1 g/100 ml.).2. When the bathing solution was distilled water, 8-arginine vasotocin was the most potent, 0.14 nmole/kg augmenting the rate of fluid uptake by 50%. Compared with it the others had relative potencies of: 8-arginine vasopressin 0.8, 8-lysine vasopressin 0.8 x 10(-3), oxytocin 0.8 x 10(-3), 8-ornithine oxytocin 0.8 x 10(-2), 8-ornithine vasopressin < 1.4 x 10(-4).3. When the bathing solution contained 0.1% NaCl, 8-arginine vasotocin was again the most potent, 0.06 nmole/kg augmenting the rate of fluid uptake by 50%. Compared with it the others had relative potencies of: 8-arginine vasopressin 0.3, 8-lysine vasopressin 0.3 x 10(-3), oxytocin 0.3 x 10(-2), 8-ornithine oxytocin 0.8 x 10(-2), 8-ornithine vasopressin < 0.6 x 10(-4).4. Dose-response curves for each peptide showed that in the case of 8-arginine vasopressin, 8-lysine vasopressin and 8-ornithine vasopressin the augmentation of rate of fluid uptake did not differ in the absence or in the presence of NaCl in the bathing solution; whereas in the case of 8-arginine vasotocin, oxytocin, and 8-ornithine oxytocin the augmentation was greater in the presence of sodium chloride.5. Support has been found for the postulate of a binary action of some neurohypophysial peptides on amphibian skin, arginine in position 8 being correlated with hydrosmotic effect, and isoleucine in position 3 with natriferic effect.
D000818:Animals; D001001:Anura; D001693:Biological Transport, Active / Q000187:drug effects; D005260:Female; D008297:Male; D010121:Oxytocin / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology*; D010539:Permeability; D010909:Pituitary Hormones, Posterior / Q000494:pharmacology*; D012869:Skin Absorption / Q000187:drug effects*; D012964:Sodium / Q000378:metabolism*; D014667:Vasopressins / Q000494:pharmacology; D014668:Vasotocin / Q000494:pharmacology; D014867:Water / Q000378:metabolism*
D010455:Peptides; D010909:Pituitary Hormones, Posterior; D014867:Water; D014667:Vasopressins; D010121:Oxytocin; D012964:Sodium; D014668:Vasotocin